The "kiln" testnet is currently running and will carry out the merge in the next few days, which is the final step before the existing proof of work testnets transitioned to proof of stake and then the Ethereum mainnet itself. I think that counts as "obvious evidence".

> with no obvious evidence that it is any closer to implemented today than it was 3 years ago.

Apart from a working PoS beacon chain, several multi client dev nets and the last merge testnet before the real merge (barring major bugs) currently running